Solar thermal panels

ABSTRACT

Systems and methods for employing solar thermal energy for heating are disclosed. In some embodiments, a system is disclosed, in which a thermal-fluid-filled solar-thermal panel that has been sealed to prevent leakage of the thermal fluid. In other embodiments, a method of sealing a solar thermal panel is disclosed. In one preferred embodiment, the solar thermal panel is sealed by applying heat to one edge of the solar thermal panel, thereby melting the edge and forming a seal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication Ser. No. 61/381,545, having the title “Solar ThermalSystem,” filed 2010 Sep. 10, which is incorporated herein by referencein its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to solar thermal panels and,more particularly, to systems and methods for manufacturing and sealingsolar thermal panels.

BACKGROUND

Collecting the sun's energy with solar panels for use in home heatingand water heating is a concept that has previously been explored andimplemented. However, most currently-existing designs focus onefficiency, rather than cost. As a result, solar thermal panels have notgained widespread use. Thus, a heretofore unaddressed need exists in theindustry to address the aforementioned deficiencies and inadequacies.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a diagram that shows one embodiment of a solar thermal system.

FIG. 2 is a front profile view of a solar thermal panel.

FIG. 3 is a side profile view of a solar thermal panel.

FIG. 4 is a side profile view of a solar thermal panel being sealed.

FIG. 5 is a perspective view of a solar thermal panel.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference is now made in detail to the description of the embodiments asillustrated in the drawings. While several embodiments are described inconnection with these drawings, there is no intent to limit thedisclosure to the embodiment or embodiments disclosed herein. On thecontrary, the intent is to cover all alternatives, modifications, andequivalents.

Brief Overview

The present disclosure teaches various systems and methods relating tosolar thermal panels and solar thermal systems. Unlike conventionalsolar thermal panels, various embodiments of the inventive solar thermalpanels are cost-effective to manufacture, thereby allowing for massproduction of the solar thermal panels. In some embodiments, a method ofsealing a solar thermal panel is disclosed. In one preferred embodiment,the solar thermal panel is sealed by applying heat and pressure to oneedge of the solar thermal panel, thereby melting the edge and forming aseal. In other embodiments, a system is disclosed, in which athermal-fluid-filled solar-thermal panel that has been sealed byapplying heat to its edge to prevent leakage of the thermal fluid.

Previous Failed Attempts and Eventual Success

Before describing the various embodiments of the invention, it isworthwhile to understand how the inventive solar thermal panels andsystems were developed, along with the corresponding processes formanufacturing these panels and systems. Although the inventive solarthermal panel and its method of manufacture may appear simple, numerousfailed attempts prior to the eventual success in building the disclosedworking models demonstrate the non-trivial nature of the inventive solarthermal panels, systems, and methods. Consequently, one having ordinaryskill in the art will appreciate the difficulties associated withmanufacturing the disclosed solar thermal panels and systems.

A particularly challenging problem related to properly sealing the panelto prevent leakage of the thermal fluid from the solar thermal panel. Asone can imagine, in order to maximize the heat capacity within the solarthermal system, much (if not all) of the thermal fluid should bemaintained within the solar thermal panel. Unfortunately, if there areleaks in the solar thermal panel, then the thermal fluid can escape,taking with it any heat that is stored in the thermal fluid.

Sealing the solar thermal panel posed a particularly difficult problemthat was not easily overcome. For example, U.S. Pat. Nos. 4,114,597 and4,178,914 describe headers for unitary solar collectors. These headersare separate components that are attached to the outside of the unitarysolar collector. Attempting to attach separate headers to the outside ofthe solar thermal panel posed problems because the interface between theheaders and the unitary solar collector, if not perfectly sealed,created points-of-failure where the thermal fluid escaped from thesystem. All attempts to externally seal the solar thermal panel withthis separate and distinct component (such as a header or a pipe)resulted in incomplete seals, which consequently resulted in leakage ofthermal fluid from the system. This occurred despite numerous attemptswith many different types of sealants and adhesives. Thus, while it mayappear trivial to externally seal the solar thermal panel, the realityof employing a separate component to achieve a leak-resistant sealproved to be unworkable.

Moving away from a separate header that attached to the outside of thesolar thermal panel, attempts were also made to seal the solar thermalpanel by removing a portion of the inner channel to create a cavity, andthen friction-fitting a pipe in the resulting cavity and sealing theinterface between the pipe and the wall of the solar thermal panel.Although intuition suggests that both friction and a commercial sealant,when used in conjunction, would provide a leak-resistant seal, all ofthe attempts to achieve a leak-resistant seal in this manner alsofailed. The point of failure was, again, the interface between the solarthermal panel and the inner pipe. Again, all attempts using a separateand distinct component resulted in incomplete seals, which againresulted in leakage of thermal fluid from the system. Despite numerousattempts with varying combinations of pipe sizes and sealants, aleak-resistant seal was never achieved. In other words, employing thisseparate internal component did not achieve a leak-resistant seal.Mainly, the seals were the points-of-failure because the entire lengthof the solar thermal panel needed to maintain the seal. Thus, overmultiple heating-cooling cycles, the solar thermal panel would expandand contract, thereby causing the adhesive (which expanded and shrank ata different rate) to fail and no longer maintain a leak-resistant seal.

Many other attempts were made to create a leak-resistant seal, thosealso failed.

Insofar as sealing the solar thermal panel with a separate componentresulted in failures, despite the numerous permutations of pipe sizesand sealing compounds, efforts were directed to finding ways to seal thesolar thermal panel without the use of separate components. Eventually,attempts were made to achieve a leak-resistant seal by melting the openends of the solar thermal panel, rather than employing separate anddistinct sealing components. Early attempts included melting the edge ofthe solar thermal panel by applying heat to the edge. While applyingheat to the edge of the solar thermal panel may seem trivial, even thismethod posed challenges. For example, finding the right conditions underwhich a proper seal would form was not a trivial task.

In terms of heat exposure, prolonged exposure caused not only the edgeof the solar thermal panel to melt, but also caused the internal ribsand layers to melt, thereby resulting in an internal leakage of thermalfluid from one layer to another. In terms of finding the correcttemperature, if the applied heat was insufficient, then the edges wouldnot melt together. Conversely, if the applied heat was too high, thenundesirable effects were seen, such as the melting of the internal ribsand layers as well as material breakdown. Additionally, when there wasuneven heat distribution, this resulted in non-uniform melting of theedges, thereby creating an unsightly solar thermal panel.

Persistence in view of all of those failures eventually led to aredirection of research efforts to the panels, methods, and systems thatare described with reference to FIGS. 1 through 5. In other words, theembodiments of the invention, as herein described, are the result ofnumerous failures and difficulties, all of which may appear trivial inhindsight, but which were in reality extraordinarily difficult toovercome.

Various Embodiments

With these difficulties in mind, attention is turned to FIGS. 1 through5, which show preferred embodiments of a solar thermal panel, a solarthermal system employing the solar thermal panel, and methods formanufacturing the solar thermal panel.

FIG. 1 is a diagram that shows one embodiment of a solar thermal system.While the system of FIG. 1 shows a closed loop that circulates thermalfluid 2, it should be appreciated by those having skill in the art thatthe system may also be configured as an open-loop system.

The system, as shown in FIG. 1, comprises a closed loop that circulatesthermal fluid 2. This closed loop includes a solar thermal panel 1 a, acontrol unit 5, a storage tank 3, and a first pump 4. The solar thermalpanel 1 a comprises a panel temperature gauge 7, which measures thetemperature of the fluid 2 within the solar thermal panel 1 a. Thestorage tank 3 comprises a fluid temperature gauge 6, a heat exchanger12, a cold water inlet 11, and a hot water pipe (not labeled). Thecontrol unit 5 is operatively coupled to the first pump 4, the paneltemperature gauge 7, and the fluid temperature gauge 6.

In operation, the thermal fluid 2 circulates through the solar thermalpanel 1 a, where the fluid 2 absorbs solar energy and heats up as aresult. The thermal fluid 2 can reach temperatures up to 150 degreesFahrenheit, which is typical for hot water heaters. Based on thereadings of the panel temperature gauge 7 and the fluid temperaturegauge 6, the control unit 5 will either activate or deactivate the firstpump 4. For example, when the reading of the panel temperature gauge 7is higher than the reading of the fluid temperature gauge 6, the controlunit 5 will activate the first pump 4, which pumps the thermal fluid 2from the tank 3 to the solar thermal panel 1 a.

The storage tank 3 receives cold water through a cold water inlet 11,and the cold water is pumped through the heat exchanger 12. As the coldwater travels through the heat exchanger 12, the temperature differencebetween the cold water and the thermal fluid 2 causes the cold water toheat, while simultaneously causing the heated thermal fluid 2 to cool.The heated water exits through the hot water pipe (not labeled). Thefirst pump 4 circulates the cooled thermal fluid 2 back to the solarthermal panel 1 a, where the fluid 2 absorbs solar energy and heats up,thereby repeating the cycle.

For some embodiments, such as the one shown in FIG. 1, the hot waterpipe (not labeled) of the storage tank 3 is operatively coupled to abooster heater 13, which includes a hot water outlet 14. For thoseembodiments, the hot water pipe (not labeled) provides the heated waterto the booster heater, which further heats the water. That water canthen be used by drawing it from the hot water outlet 14.

In addition to using the thermal fluid 2 to heat water for use, thesystem of FIG. 1 also shows a closed loop in which the thermal fluid 2is used for space heating. An exemplary system for space heatingcomprises a booster heater 13, a second pump 9, an ambient temperaturegauge 10, and a hydronic heating system 8. The second pump 9 and theambient temperature gauge 10 are operatively coupled to the control unit5, which activates or deactivates the second pump 9 based on the readingof the ambient temperature gauge 10.

In operation, when the reading of the ambient temperature gauge 10 isbelow a set thermostat temperature, the control unit activates thesecond pump 9, thereby circulating the heated thermal fluid 2 from thestorage tank 3 to the booster heater 13. The booster heater 13 furtherheats the thermal fluid 2, which is then pumped through the hydronicheating system 8 via the second pump 9. As the fluid 2 travels throughthe hydronic heating system 8, it cools as a result of heat transfer tothe heated space. The cooled thermal fluid 2 is then pumped back to thestorage tank 3, where the cycle may repeat.

As one can appreciate, the efficiency of the entire system depends inlarge part on the efficiency of the solar thermal panel 1 a, whichallows the thermal fluid to collect and store the solar thermal energy.Having described the system, the solar thermal panel 1 a of FIG. 1 isdescribed in greater detail with reference to FIGS. 2 through 5.

FIG. 2 is a front profile view of a preferred embodiment of the solarthermal panel 1 a of FIG. 1.

As shown in FIG. 2, the solar thermal panel 1 a comprises horizontallayers 15 a, 15 b, 15 c (collectively 15), which horizontally separatethe internal space within the solar thermal panel 1 a into top channels17 and bottom channels 18. Preferably, these layers comprise clearpolymer material that allows a large percentage of solar radiation topass through the layers 15. The solar thermal panel 1 a also comprisesvertical ribs 16, which vertically separate the internal space withinthe solar thermal panel 1 a into channels that carry the thermal fluid 2through the solar thermal panel 1 a. Preferably, the solar thermal panel1 a is placed above a solid structure, such as a residential roof (notshown). To increase the heat absorption by the thermal fluid 2, and alsoto reduce heat loss from a residential structure, the bottom of thesolar thermal panel 1 a can be coated with an absorbing layer 19, andthe solar thermal panel 1 a can be placed above an insulating layer 20.

Given this multi-layered structure, the solar thermal panel 1 a carriesthe thermal fluid 2 through its bottom channels 18. The top channels 17act as both a transmissive layer and an insulating layer. In otherwords, the air gap within the top channels 17 allow for transmission ofsolar radiation while simultaneously providing insulation to the bottomchannels 18. For some embodiments, the top channels 17 can be evacuatedto provide a partial vacuum, thereby improving the solar thermal panel'sinsulation properties. Once the solar radiation reaches the absorbinglayer 19, the solar radiation is converted to thermal energy. Thethermal energy is then absorbed by the thermal fluid 2, which is carriedin the bottom channels 18 adjacent to the absorbing layer 19. The heatedthermal fluid then circulates through a solar thermal system, similar tothat shown in FIG. 1.

As one having skill in the art can appreciate, the solar thermal panel 1a is sealed in such a way that the thermal fluid 2 does not undesirablyleak out of the system. Attention is now turned to processes formanufacturing sealed solar thermal panels.

FIG. 3 is a side profile view of a solar thermal panel as it ismanufactured through an extrusion process. Specifically, the solarthermal panel comprises an extruded polymer sheet 1 d. One particulartype of multi-layered extruded polymer sheet is LEXAN®, a product fromGeneral Electric Company. As shown in FIG. 3, when the extruded polymersheet 1 d is extruded in accordance with known methods, the resultingsheet comprises multiple layers 15 a, 15 b, 15 c, which define topchannels 17 and bottom channels 18. Since the process of extrudingmulti-layered polymer sheets is well known in the art, furtherdiscussion of that particular process is omitted here.

FIG. 4 is a side profile view of a solar thermal panel 1 c being sealed.As noted above, although the process of fabricating an extruded polymersheet 1 d is widely known in the industry, the process of sealing theextruded polymer sheet 1 d is non-trivial. FIG. 4 shows one embodimentof a process for manufacturing a sealed extruded polymer panel 1 c.

In a preferred embodiment, the extruded polymer panel 1 c is sealed asit emerges from the extrusion process. As the extruded polymer panel 1 cpasses over a bottom die 22, a heating die 21 is applied in a directionthat is vertical to the extruded polymer panel 1 c, thereby creating animpact seal 23, which melts the extruded polymer panel 1 c at the pointof impact to create a sealed edge.

As described above, the temperature of the heating die 21, the heatdistribution within the heating die 21, and the speed at which theheating die 21 is applied should be controlled so as to provide a properseal. Specifically, the heating die 21 should be at a temperature thatis slightly higher than the melting temperature of the polymer material,but not so high as to char or burn the polymer material. Also, theheating die 21 should be uniformly heated in order to avoid non-uniformmelting of the extruded polymer panel 1 c. Finally, the rate at whichthe heating die 21 is applied should be sufficiently slow enough thatthe extruded polymer panel 1 c melts, rather than being crushed by theweight of the heating die 21. Insofar as all of these factors depend onthe characteristics of the polymer material, and insofar as one havingskill in the art can calculate these factors, further discussion ofapplying the heating die 21 is omitted here. It should also beappreciated by those skilled in the art that the heat-sealing of theextruded polymer panel 1 c can be done by other forms of conduction,convection heating, radiant heating, or various combinations thereof.Thus, for example, should the extruded polymer panel not be sealedimmediately after extrusion, a different manufacturing process usingconduction, convection, or radiation may be employed to achieve the sealafter the extrusion process.

The polymer panel 1 c, once sealed, now provides a base from which afunctional solar thermal panel can be fabricated. One such panel isshown with reference to FIG. 5.

FIG. 5 is a perspective view of a functional solar thermal panel 1 b,which has been fabricated from the sealed extruded polymer panel 1 c ofFIG. 4. Specifically, FIG. 5 shows a solar thermal panel 1 b, with afirst set of holes 24 a associate with an inlet 25 a, and a second setof holes 24 b, associated with an outlet 25 b. One can readilyappreciate that the inlet 25 a and the outlet 25 b may be reversed,depending on the direction of the flow of the thermal fluid 2. The firstset of holes 24 a are drilled through the bottom channels 18 (FIG. 2)near a distal edge of the solar thermal panel 1 b, and the inlet 25 a isconnected to the first set of holes 24 a. The second set of holes 24 bare drilled through the bottom channels 18 (FIG. 2) near a proximal edgeof the solar thermal panel 1 b, and an outlet 25 b is connected to thesecond set of holes 24 b. In preferred embodiments, the holes 24 a, 24 bare located approximately one inch from their respective edges.

In operation, the inlet 25 a allows for entry of thermal fluid 2 (FIG.2) into the solar thermal panel 1 b. Once the thermal fluid 2 enters thesolar thermal panel through the inlet 25 a, the fluid travels throughthe bottom channels 18 (FIG. 2) of the solar thermal panel 1 b.Eventually, the fluid 2 fills the bottom channels 18 of the solarthermal panel 1 b and is expelled through the outlet 25 b.

Placing this in the context of FIG. 1, the fluid that gets pumped intothe solar thermal panel 1 a by the first pump 4 will enter the solarthermal panel 1 a through the inlet 25 a. Consequently, once that fluid2 has traveled through the solar thermal panel 1 a and has been heatedby the solar radiation, the fluid 2 is expelled through the outlet 25 band pumped to the storage tank 3.

As shown in FIG. 1, the solar thermal panel 1 a can be attached to aresidential roof, or mounted on walls, or can be used in any positionthat is consistent with the desired purpose. Typically, polymermaterials, such as LEXAN®, have an estimated life of 30 years. Thesetypes of solar thermal panels can be configured for use in existingstructures, or as roofing materials for new structures.

Variants

Although exemplary embodiments have been shown and described, it will beclear to those of ordinary skill in the art that a number of changes,modifications, or alterations to the disclosure as described may bemade. For example, while a residential roofing system has been describedwith reference to the solar thermal panels, it should be appreciatedthat the system can be used in residential, commercial, or industrialsettings. Additionally, one having skill in the art will understand thatthe system of FIG. 1 can be configured to be wholly programmable andautomated, or can require manual input by a user. Also, one having skillin the art will understand that the thermal fluid can be water, glycol,or other fluid that has desired heat capacity properties. Furthermore,one having skill in the art will appreciate that the absorbing layer 19can comprise tar paper, paint, or other substance that is conducive toabsorbing solar energy. Finally, it should be appreciated that, whileFIG. 1 shows an embodiment that employs pumps 4, 9 to transport thefluid 2, a wholly passive system that is based on thermal convection canbe used to transport the thermal fluid 2.

All such changes, modifications, and alterations should therefore beseen as within the scope of the disclosure.

What is claimed is:
 1. A method of manufacturing a solar thermal panel, comprising the steps of: extruding a polymer panel comprising layers, the polymer panel further comprising an open edge; and melting the open edge to form a sealed edge.
 2. The method of claim 1, wherein the melting step comprises the steps of: pressing the top of the polymer panel with a heated die, thereby causing the layers to melt together to form a seal.
 3. The method of claim 1, wherein the melting step comprises the steps of: heating the open edge with a radiative heat source.
 4. The method of claim 1, wherein the melting step comprises the steps of: heating the open edge with a convective heat source.
 5. The method of claim 1, wherein the melting step comprises the steps of: heating the open edge with a conductive heat source.
 6. A solar thermal panel manufactured using the method of claim
 1. 7. A solar thermal panel comprising: a bottom channel for carrying thermal fluid, the bottom channel having a bottom-channel seal to prevent leakage of the thermal fluid from the bottom channel; a first hole located near a first edge of the bottom channel, the first hole for receiving the thermal fluid from an external source; a second hole located near a second edge the bottom channel, the second hole for expelling the thermal fluid from the solar thermal panel; and a top channel located above the bottom channel, the top channel having a top-channel seal.
 8. The panel of claim 7, further comprising: an inlet attached to the first hole; and an outlet attached to the second hole. 